change logic to avoid filtering off the captured item

cucumber-expressions/javascript/src/Group.ts

@@ -8,7 +8,7 @@ export default class Group {
 
   get values(): string[] {
     return (this.children.length === 0 ? [this] : this.children)
+      .filter(g => typeof g.start !== 'undefined')
       .map(g => g.value)
-      .filter(v => v !== null)
   }
 }